Shielded cable



May 15, 1934.

l.. c. woLcoTT 1,958,687

SHIELDED CABLE Filed March 25. 1931 Patented May I5, 1934 UNITED STATES PATENT'- oFFlca smELDEn CABLE Application March 25, 1931, Serial No. 525,115

4 Claims. (Cl. 173-264) ing must be grounded at frequent intervals along its length. If this is not done noise in the rel5 ceiver will develop Where the shielding touches the metal of the motor due to the discharge to ground of the induced voltages in the shield. Furthermore, oil, grease, gasoline, and moisture easily penetrate the wire braid ordinarily used for shielding ignition cable and this reduces the eiciency of the shield and shortens the effective life of the insulation on the cable. Also, with the wire braid'exposed, it is subject to mechanical damage which tends to reduce the eiiiciency of the shield and also damages-the insulation of the cable.

Another factor that has led to comparatively rapid deterioration 'of the rubber insulation of the cable has been the corona effect which forms ozone in the air surrounding the insulation and this ozone attacks the rubber and deteriorates its insulating qualities.

` It is one of the objects of the invention to provide a cable that will be so constructed as to largelyovercome the objections tof'such cables as heretofore manufactured. It is a further object of the invention to provide a cable that will not require grounding of the shield at frequent intervals and, in the use of which, it will only be necessary to ground the shield at the ends of the cable. A further obiect of the invention is to provide a construction that will be practically impervious to salt water, oil, and air so as to avoid the above mentioned deteriorating eiects of these on the 'rubber insulation of the cable.

Other objects of the invention and the features ot novelty will be app'arent from the following description taken in connection with the accomrallying drawing, oi.' which Fig. 1 is an enlarged view of a cable constructed in accordance with my invention, diiferent parts of the cable beingbroken away to disclose other parts; and

- Fig. 2 is a cross-section ofta multiple conductor cable embodying my'invention.

Referring to the drawing, 10 indicates the usual metallic conductor of the cable which is surrounded by an insulating covering il of rubber. Surrounding the rubber 11 is a fabric covering 12 in the form of a braid, such as iscommonly used on automotive cables. The braid 12 is given several coats of lacquer, or a suitable varnish, as indicated at 13, to render the braid 12. impervious to water, oil and air. As a further insulation and protection, a tape 14 may be wound over the lacquer coating 13- although, in some instances, the tape'14 may be omitted.

A metallic shield 15 is then applied over the tape 14 or, if the tape 14 is not used, the metallic shield 15 is placed directly over the lacquered braid l2. The shield 15 is in the form ci a closely woven braid of iat Wires so as to give flexibility. A fabric braid i6 is then woven overthe metallic braidland the braid 16 is given several coats of lacquer or a suitable varnish, as indicated at i7.

The different layers of fabric and metal, surrounding the insulation l1., are each tightly applied to the layer underneath so that the coverings will be practically devoid of air and, therefore, there will be no opportunity for the forniation of ozone in the coverings,

The braid 16, with the coating 17 thereon. serves as an insulation for the metallic braid l5 and the coating 17 renders the braid 16 impervious to water, oil and air. By thus insulating the metallic shield it is not necessary to ground this shield elsewhere than at the ends of the cable because the braid 16 so insulates the shield that the localized E. M. Fis that are generated in the shield have no opportunity of forming sparks when the cable touches a metallic part.

Referring to Fig. 2, a plurality-of insulated ccnductors are indicated at 18 and the insulation for these conductors preferably consists of a rubber covering such as is indicated at l1 in Fig, i, and this rubber covering is surrounded by a lacquer covered braid such as that indicated at 12. This lgroup of insulated conductors 18' is surrounded by a metallic braid 19, similar to the braidd,

and this metauic braid is surrounded by a rabic braid 20 which has a lacquer coating 21.

A cable constructed as described has all of the4 advantages ofv prior constructions and' has the additional advantage of much longer life and opmetallic conductor surrounded by a covering of lil lli)

rubber insulation, a plurality of layers of insulating fabric surrounding said rubber insulation, a iiexible metallic shield surrounding said insulating fabric, and a lacquer coated Woven fabric surrounding said shield.

4. An ignition cable consisting of a plurality of conductors each of which is surrounded by a covering of rubber insulation having a water-tight and air-tight fabric thereon, said plurality of conductors being enclosed in a flexible metallic shield and said flexible metallic shield being surrounded by a water-tight and air-tight fabric covering.

LESLIE C. WOLCOTT. 

